The term "polyphenylene oxide resin" includes a family of polymers that are well known to those skilled in the art. These polymers may be made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration certain of the polyphenylene oxides are disclosed in Hay, U.S. Pat. No. 3,306,874 and 3,306,875, and in Stamatoff, 3,257,357 and 3,257,388. In the Hay patents the polyphenylene oxides are prepared by an oxidative coupling reaction comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes for preparing polyphenylene oxide polymers including graft copolymers of polyphenylene oxides with styrene type compounds, are found in Fox, U.S. Pat. No. 3,356,761; Sumitomo, U.K. Pat. No. 1,291,609; Bussink et al; U.S. Pat. No. 3,337,449; Blanchard et al, U.S. Pat. No. 3,219,626; Laakso et al, U.S. Pat. No. 3,342,892; Hori et al, U.S. Pat. No. 3,384,619; Faurote et al, U.S. Pat. No. 3,440,217; and disclosures relating to metal based catalysts which do not include amines, are known from patents such as Wieden et al, U.S. Pat. No. 3,442,885 (copper-amidines); Nakashio et al, U.S. Pat. No. 3,573,257 (metal-alcoholate or phenolate); Kobayashi et al, U.S. Pat. No. 3,445,880 (cobalt chelates); Olander, U.S. Pat. No. 3,956,242 and the like. In the Stamatoff patents, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as peroxy acid salt, an acid peroxide, a hypohalite and the like, in the presence of a complexing agent. Disclosures relating to non-catalytic processes, such as oxidation with lead dioxide, silver oxide etc., are described in Price et al, U.S. Pat. No. 3,382,212. Cizek, U.S. Pat. No. 3,383,435 discloses polyphenylene ether-styrene resin compositions. All of the above-mentioned disclosures are incorporated herein by reference. In Ser. No. 401,994, filed Oct. 1, 1973, a process is described for preparing compositions of a polyphenylene oxide, a rubber and an alkenyl aromatic monomer. An analogous process is described in Ser. No. 401,987 filed Oct. 1, 1973. These processes are based on the use of the alkenyl aromatic monomers as the reaction solvents for a phenolic monomer. After the polyphenylene oxide is formed, the alkenyl aromatic monomer is polymerized to an alkenyl aromatic resin by a free radical catalyst. Thermal polymerization of the alkenyl aromatic monomer is also mentioned in these applications.
The present invention is based on the discovery that the use of a capped polyphenylene oxide in a process wherein an alkenyl aromatic monomer is polymerized in the presence of a polyphenylene oxide, results in a composition wherein the alkenyl aromatic polymer has a higher molecular weight as compared with a composition prepared under similar conditions with an uncapped polyphenylene oxide.
Accordingly, it is a primary object of this invention to provide an improved process for the preparation of a composition of a polyphenylene oxide resin and a styrene resin.